1. Field of the Invention
The invention relates generally to arc lamps, and specifically to components and methods used to reduce the cost of manufacturing xenon arc lamps.
2. Description of the Prior Art
Short arc lamps provide intense point sources of light that allow light collection in reflectors for applications in medical endoscopes, instrumentation and video projection. Also, short arc lamps are used in industrial endoscopes, for example in the inspection of jet engine interiors. More recent applications have been in color television receiver projection systems and dental curing markets.
A typical short arc lamp comprises an anode and a sharp-tipped cathode positioned along the longitudinal axis of a cylindrical, sealed concave chamber that contains xenon gas pressurized to several atmospheres. U.S. Pat. No. 5,721,465, issued Feb. 24, 1998, to Roy D. Roberts, describes such a typical short-arc lamp. A typical xenon arc lamp, such as the CERMAX marketed by ILC Technology (Sunnyvale, Calif.) has a three-legged strut system that holds the cathode electrode concentric to the lamp""s axis and in opposition to the anode.
The manufacture of high power xenon arc lamps involves the use of expensive and exotic materials, and sophisticated fabrication, welding, and brazing procedures. Because of the large numbers of xenon arc lamps being produced and marketed, every opportunity to save money on the materials and/or assembly procedures is constantly being sought. Being the low-cost producer in a market always translates into a strategic competitive advantage.
For example, the CERMAX-type arc lamp 100 shown in FIG. 1 is a common type sold in the commercial market. The manufacturing of lamp 100 can easily cost the biggest part of one hundred dollars for material and labor. The total manufacturing costs set the minimum amount that can be charged at retail, so the production volumes that can be sold are limited by the high price points that must be charged. The lamp 100 is conventional and comprises an optical coating 102 on a sapphire window 104, a window shell flange 106, a body sleeve 108, a pair of flanges 110 and 112, a three-piece strut assembly 114, a two percent thoriated tungsten cathode 116, an alumina-ceramic elliptical reflector 118, a metal shell 120, a copper anode base 122, a base support ring 124, a tungsten anode 126, a gas tubulation 128, and a charge of xenon gas 130. All of which are brazed together in several discrete brazing operations.
It has been discovered by the present inventors, Roberts and Manning, that cathode electrodes that are attached to one side or the other of a supporting strut will experience a deflection of the distal arc-end to one side of the anode during operation. What is needed is a construction and method that provide for a stabilized cathode electrode position during operation.
It is therefore an object of the present invention to provide a xenon ceramic lamp that is less expensive to produce than conventional designs.
It is another object of the present invention to provide a low-cost xenon ceramic lamp that works equally as well as more expensive conventional designs.
Briefly, an arc lamp comprises a single edge-to-edge cathode support strut on which the cathode is mounted with an end slot. Such makes heat loading on the assembly symmetrical over operational time, and arc tip wander from the anode center is practically eliminated. Nine component parts that are brought together in only three brazes and one TIG-weld to result in a finished product. An anode assembly is brazed with the rest of a body sub-assembly in one step instead of two. A single-bar cathode-support strut is brazed together as one step. A window flange and a sapphire output window are brazed together with the product of the strut braze step in a mounted-cathode-braze step. A copper-tube fill tubulation, a kovar sleeve, a ceramic reflector body, an anode flange, and a tungsten anode are all brazed together in a xe2x80x9cbody-brazexe2x80x9d step. The products of the mounted-cathode-braze step and body-braze step are tungsten-inert-gas (TIG) welded together in a final welding step. A lamp is finished by filling it with xenon gas and pinching off the tubulation.
An advantage of the present invention is that a ceramic arc lamp is provided that is less expensive to manufacture compared to prior art designs and methods.
Another advantage of the present invention is that a ceramic arc lamp is provided that is simple in design.
A further advantage of the present invention is that a ceramic arc lamp is provided that has a single-bar cathode-support strut.
A still further advantage of the present invention is that a ceramic arc lamp is provided that requires fewer sub-assemblies.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the drawing figures.